Electromagnetically operated holding devices



United States Patent This invention relates to an electromagnctically operated tool-holding or work-holding device. In the use of tablesaws, lathes, milling machines, drill presses, planers, and other machine tools, it is frequently necessary to set up or position the work relatively to the tool and s secure the adjustable article, whether it be the work or the tool, in place. The use of mechanical clamps for this purpose is often bothersome, if not for some reason impossible. Moreover, it is'often impossible to employ in such cases mechanical clamps operating in planes normal to each other.

It is known that electro-mechanically operated clamps have been devised in the'pastfor clamping a workpiece or tool in operative position. Prior devices, each provided with a work or tool engaging clamp member, have operated on the principle of an electromagnetic attraction between the clamp and a magnetizable support, such as the iron or steel worktable of a machine tool. How-" ever, prior electromagnetic holding devices have been open to various objections.

One object of the invention is to provide an improved electromagnetically operated tool-holding or work-holding device. l

' Another object is to provide a device suchas characterized above, which is provided with two clamp members, both engageable with the adjustable article to secure it in two planes normal to each other.

Still anotherobject is to provide a holding device, such as characterized above, in which one of the clamp membersis angularly and axially adjustable, as well as adjustable from one station to another, and is releasably held in adjusted position by electromagnetic forces.

In the drawing:

FIG. 1 is a fragmentary plan view illustrating a magnetically operated holding device embodying the invention and showing the device in association with a tablesaw;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is an enlarged bottom view of the device;

FIG. 4 is an enlarged sectional view taken on line 4-4 of FIG. 2;

FIG. 5 is a view illustrating a simple wiring diagram for the device; and

FIG. 6 is an enlarged sectional view taken on line 6-6 of FIG. 2.

In the drawing, the electromagnetically operated holding device is indicated generally at 10, and the tablesaw is indicated generally at 11. The tablesaw, which is illustrated only by way of example, is provided with the usual tabletop 12 supported in a conventional manner, and a radial saw 13, driven from a conventionally supported electrical motor 14, extends through the tabletop 12 in the usual manner for engagement with the work 15. The tabletop is provided with the usual adjustable fence 16 for engagement with the work to support the latter against lateral dislocation in one direction. The holding device serves to hold the work down on the tabletop 12, and also serves to hold the work against lateral dislocation in the opposite direction.

The holding device includes a case 17 of box-like form constructed of non-magnetic material. The case, which may be conveniently formed of plastic material, is illustrated as being of oblong form, having upstanding side walls and end walls and a top integral with these walls, the bottom of the case being open. The case 17 receives through its open bottom a flux-carrying body member indicated generally at 18, which may be formed conveniently of mild steel. The body member is provided with a central core element 19, and at each end of the member 18 there is provided a pole piece 20 having its upper extremity interconnected with the core element 19 by a horizontally extending portion of the body member 18. In the illustrated embodiment the pole pieces 20 are formed integrally with the core and the body member is generally of E shape, the pole pieces being at the ends of the E and the core element being in the center. The body member 18 is supported in the case 17, as by suitable fasteners 21 extending into the last-named member through the top of the case, and the body member is arranged in the case in such a manner that both pole pieces 20 and the core element 19 are substantially flush with the lower extremity of the case to engage the tabletop 12.

The body member 18 is provided with lugs or ears 22 at the respective ends of the last-mentioned member, and these are formed in the illustrated embodiment as integral parts of the body member. A' coil 23 formed of a multiplicity of turns of an insulated copper wire embraces the core element 19 and is suitably secured to the body member in upwardly spaced relation' to the open lower extremity of the case. As best shown in FIG. 3, the lower extremities of the pole pieces 20 which engage the tabletop are provided with circular grooving 24 and, as shown in this view, the lugs or cars 22 of the body member are elongated transversely of the case.

Each ear has an end closely approaching one side wallj of the case, and each ear is provided with a longitudinal bore 25 extending therethrough. The side walls of the case are provided with openings 26 in alignment with the respective bores, so thateither bore may receive rather snugly a rod 27 which may extend through the case and. which issaxially adjustable. in the bore and also'axially' A make-and-break switch 28 may be mounted con-'- "1 veniently. onithe top of the case to control thecircuit in which the coil 23 is interposed, a simple circuit for the electromagnetically operated holding device being illustrated in FIG. 5 by way of example. The holding device may be connected through a conventional plug, not shown, to ordinary alternating household current. The circuit shown in FIG. 5 includes a voltage-reducing resistor 29 and a series of rectifiers 30 to convert the alternating current to direct current. When the circuit is closed by the switch 28, current flowing through the coil 23 may create a flow of magnetic flux in the core element 19 in a downward direction, creating a strong magnetic attraction of the holding device to the tabletop 12 to firmly fix the device in place, and the magnetic flux may fiow from the element 19 through the tabletop to the pole pieces 20 and through these pieces back to the core element 1 9, creating a magnetic attraction between the pole pieces and the tabletop. The flow of flux is such that some of the flux flows through the cars 22 to create a magnetic attraction between the rod 27 and either ear receiving it to not only secure the rod in an angularly adjusted position, but also secure the rod in any axially adjusted position thereof. One end of the rod is provided with a work-holding shoe 31 fixed thereto and preferably formed of a strap of spring steel having a rounded end 32 to press downwardly on the work. When the circuit is opened by the switch 28 and the electromagnet is de-energized, the work-holding shoe 31 may be adjusted toward or away from the fence 16 of the tablesaw by a sliding movement of the rod 27 and, as shown in FIG. 1, the shoe-carrying rod may be removed from its full line position in which it extends amass;

through one of the ears 22 and may be placed in the broken line position in which it extends through the other ear 22. This permits the shoe to be adjusted lengthwise of the work. Moreover, the work-engaging part 32 of the shoe may be adjusted upwardly and'downwardly by angular adjustment of the rod 27 in either ear 2-2. In this connection, the work-engaging part 32 is shown in full lines in FIG. 6 in a relatively elevated position, while in the same view it is shown in a somewhat lower position in broken lines. If desired, the hold-down element, that is, the shoe-carrying rod 27, may be removed from the electromagnetically operated holding device and the device operated without the hold-down element.

The electromagnetic holding device is provided with a work-holding shoe 33 to hold the work against the fence 16, the shoe 33 also being formed of. a strap of spring steel and having a rounded part 34 for engagement with the work. In the instant form the shoe 33 is fixed to the case 17 as by suitable fasteners 35. Thus, it will be understood that when the electromagnet is tie-energized the holding device may be adjusted toward or away from the fence 16. When the holding device is properly adjusted and the electromagnet is energized, the shoe 33 very effectively holds the work against the fence.

It will be manifest from the foregoing disclosure that there is provided in accordance with the invention a novel and superior eleotrornagnetically operated holding device. One feature of the holding device is that it is provided with two clamps or work-holding shoes, both engageable with the movable article, such as the work, for example, to secure the article in two planes normal to each other. Still another feature of the invention resides in the provision of a clamp or work-holding shoe which may occupy either of two stations or positions lengthwise of the work, as shown, and which in addition may be adjusted in and out and also adjusted angularly. It will be manifest from the foregoing disclosure that still another feature of the holding device resides in the employment of electromagnetic forces; that is, the flow of flux, to hold the last-named shoe in any of its adjusted positions. Yet another feature of the holding device is that it is constructed of few and simple parts, may be manufactured at low cost, and is very efficient in operation.

While only one form of the holding device has been illustrated in the drawing and described above, it will be apparent to those versed in the art that the holding device may take other forms and is susceptible of various changes in details without departing from the principles of the invention and the scope of the appended claims.

What I claim is:

1. In an electromagnetically operated holding device, a body of magnetizable material for resting on a support of magnetizable material, an electromagnetic coil on the body which when energized efiects the passage of flux between the support and the body to hold the latter firmly in fixed position on the support, and article-holding means of magnetizable material for support from said body and adjustable extensibly from the latter, said means also being angularly adjustable with reference to the body and receiving, when the coil is energized, flux to hold said article-holding means in fixed and adjusted position with reference to the body, the body being provided with means defining an opening into which said article-holding means extends, the last-named means comprising a rod telescopically received in said opening in the body and rotatable therein when said coil is de-energized, said article-holding means also comprising a resilient article-engaging shoe on the rod and having a generally arcuate work-engaging part at the end 'of a strap-like part extending transversely of the rod, so that said work-engaging part may be raised or lowered on rotation of said rod in the corresponding direction.

2. A holding device as defined in claim. 1 wherein an article-engaging shoe is provided in fixed relation to the body to engage the article in a plane normal to the plane of operation of the first shoe.

3. A holding device as defined in claim 2. wherein the body is elongated relatively to the support and is provided with longitudinally spaced means defining opening 5 in the body to selectively receive said rod of the articleholding means.

References Cited in the file of this patent UNITED STATES PATENTS 

